SERVICE AND TECHNICAL SUPPORT MANUAL
Gas Furnace: (F/G)9MVE
Specifications subject to change without notice.
24
440 04 4801 00
Cleaning Heat Exchangers
The following items must be performed by a qualified service
technician.
Primary Heat Exchangers
If the heat exchangers get an accumulation of light dirt or dust
on the inside, they may be cleaned by the following procedure:
NOTE
: If the heat exchangers get a heavy accumulation of
soot and carbon, both the primary and secondary heat
exchangers should be replaced rather than trying to clean them
thoroughly due to their intricate design. A build
−
up of soot and
carbon indicates that a problem exists which needs to be
corrected, such as improper adjustment of manifold pressure,
insufficient or poor quality combustion air, improper vent
termination, incorrect size or damaged manifold orifice(s),
improper gas, or a restricted heat exchanger (primary or
secondary). Action must be taken to correct the problem.
1. Turn off gas and electrical supplies to furnace.
2. Remove control door.
3. Disconnect wires or connectors to flame rollout switch,
gas valve, igniter, and flame sensor.
4. Using backup wrench, disconnect gas supply pipe from
furnace gas control valve.
5. Remove two screws attaching top filler plate and rotate
upwards to gain access to screws attaching burner
assembly to cell panel.
6. Remove screws attaching burner assembly to cell panel.
(See
Figure 10
)
NOTE
: Burner cover, manifold, gas valve, and burner
assembly should be removed as one assembly.
7. Clean heat exchanger openings with a vacuum and a
soft brush. (See
Figure 13
)
Figure 13
Cleaning Heat Exchanger Cell
NOTE
: After cleaning, inspect the heat exchangers to ensure
they are free of all foreign objects that may restrict flow of
combustion products.
8. Reverse items 6 through 1 for reassembly.
9. Refer to furnace wiring diagram and reconnect wires to
flame rollout switch, gas valve, igniter, and flame sensor.
10. Turn on gas and electrical supplies to furnace.
11. Check furnace operation through two complete heat
operating cycles. Look at burners. Burner flames should
be clear blue, almost transparent. (See
Figure 14
)
12. Check for gas leaks.
Figure 14
Burner Flame
A11461
B
urner
F
lame
B
urner
Manifold
FIRE OR EXPLOSION HAZARD
Failure to follow this warning could result in personal
injury, death, and/or property damage.
Never purge a gas line into a combustion chamber.
Never test for gas leaks with an open flame. Use a
commercially available soap solution made
specifically for the detection of leaks to check all
connections. A fire or explosion may result causing
property damage, personal injury or loss of life.
!
WARNING
13. Replace main furnace door.
Secondary Heat Exchangers
The condensing side (inside) of the secondary heat exchanger
CANNOT be serviced or inspected without complete removal of
the heat exchanger assembly. Detailed information on heat
exchanger removal can be obtained from your Distributor.
Winterization
UNIT AND PROPERTY DAMAGE HAZARD
Failure to follow this caution may result in unit
component or property damage.
If the furnace is installed in an unconditioned space
where the ambient temperatures may be 32
_
F (0
_
C) or
lower, freeze protection measures must be taken to
prevent property or product damage.
CAUTION
!
Since the furnace uses a condensing heat exchanger, some
water will accumulate in the unit as a result of the heat transfer
process. Therefore, once it has been operated, it cannot be
turned off and left off for an extended period of time when
temperatures will reach 32
_
F (0
_
C) or lower unless winterized.
Follow these procedures to winterize your furnace:
